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  <title>Registers a &quot;regular&quot; User Defined Function for use in SQL statements</title>

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</div><hr /><div id="function.sqlite-create-function" class="refentry">
 <div class="refnamediv">
  <h1 class="refname">sqlite_create_function</h1>
  <h1 class="refname">SQLiteDatabase::createFunction</h1>
  <p class="verinfo">(PHP 5 &lt; 5.4.0, sqlite &gt;= 1.0.0)</p><p class="refpurpose"><span class="refname">sqlite_create_function</span> -- <span class="refname">SQLiteDatabase::createFunction</span> &mdash; <span class="dc-title">
   Registers a &quot;regular&quot; User Defined Function for use in SQL statements
  </span></p>

 </div>

 <div class="refsect1 description" id="refsect1-function.sqlite-create-function-description">
  <h3 class="title">说明</h3>
  <div class="methodsynopsis dc-description">
   <span class="type"><span class="type void">void</span></span> <span class="methodname"><strong>sqlite_create_function</strong></span>
    ( <span class="methodparam"><span class="type">resource</span> <code class="parameter">$dbhandle</code></span>
   , <span class="methodparam"><span class="type">string</span> <code class="parameter">$function_name</code></span>
   , <span class="methodparam"><span class="type"><a href="language.types.callable.html" class="type callable">callable</a></span> <code class="parameter">$callback</code></span>
   [, <span class="methodparam"><span class="type">int</span> <code class="parameter">$num_args</code><span class="initializer"> = -1</span></span>
  ] )</div>

  <p class="para rdfs-comment">面向对象风格 (method):</p>
  <div class="methodsynopsis dc-description">
   <span class="modifier">public</span> <span class="type"><span class="type void">void</span></span> <span class="methodname"><strong>SQLiteDatabase::createFunction</strong></span>
    ( <span class="methodparam"><span class="type">string</span> <code class="parameter">$function_name</code></span>
   , <span class="methodparam"><span class="type"><a href="language.types.callable.html" class="type callable">callable</a></span> <code class="parameter">$callback</code></span>
   [, <span class="methodparam"><span class="type">int</span> <code class="parameter">$num_args</code><span class="initializer"> = -1</span></span>
  ] )</div>

  <p class="para rdfs-comment">
   <span class="function"><strong>sqlite_create_function()</strong></span> allows you to register a PHP
   function with SQLite as an <acronym title="User Defined Functions">UDF</acronym> (User Defined
   Function), so that it can be called from within your SQL statements.
  </p>
  <p class="para">
   The UDF can be used in any SQL statement that can call functions, such as
   SELECT and UPDATE statements and also in triggers.
  </p>
 </div>


 <div class="refsect1 parameters" id="refsect1-function.sqlite-create-function-parameters">
  <h3 class="title">参数</h3>
  <p class="para">
   <dl>

    
     <dt>
<em><code class="parameter">dbhandle</code></em></dt>

     <dd>

      <p class="para">
       The SQLite Database resource; returned from <span class="function"><a href="function.sqlite-open.html" class="function">sqlite_open()</a></span>
       when used procedurally.  This parameter is not required
       when using the object-oriented method.
      </p>
     </dd>

    
    
     <dt>
<em><code class="parameter">function_name</code></em></dt>

     <dd>

      <p class="para">
       The name of the function used in SQL statements.
      </p>
     </dd>

    
    
     <dt>
<em><code class="parameter">callback</code></em></dt>

     <dd>

      <p class="para">
       Callback function to handle the defined SQL function.
      </p>
      <blockquote class="note"><p><strong class="note">Note</strong>: 
       <span class="simpara">
        Callback functions should return a type understood by SQLite (i.e.
        <a href="language.types.intro.html" class="link">scalar type</a>).
       </span>
      </p></blockquote>
     </dd>

    
    
     <dt>
<em><code class="parameter">num_args</code></em></dt>

     <dd>

      <p class="para">
       Hint to the SQLite parser if the callback function accepts a
       predetermined number of arguments.
      </p>
     </dd>

    
   </dl>

  </p>
  <blockquote class="note"><p><strong class="note">Note</strong>: <span class="simpara">为兼容其他数据库扩展(比如 MySQL)，支持两种可替代的语法。推荐第一种格式，函数的第一个参数是<em><code class="parameter">dbhandle</code></em>。</span></p></blockquote>
 </div>


 <div class="refsect1 returnvalues" id="refsect1-function.sqlite-create-function-returnvalues">
  <h3 class="title">返回值</h3>
  <p class="para">
   没有返回值。
  </p>
 </div>


 <div class="refsect1 examples" id="refsect1-function.sqlite-create-function-examples">
  <h3 class="title">范例</h3>
  <p class="para">
   <div class="example" id="example-2072">
    <p><strong>Example #1 <span class="function"><strong>sqlite_create_function()</strong></span> example</strong></p>
    <div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB">&lt;?php<br /></span><span style="color: #007700">function&nbsp;</span><span style="color: #0000BB">md5_and_reverse</span><span style="color: #007700">(</span><span style="color: #0000BB">$string</span><span style="color: #007700">)&nbsp;<br />{<br />&nbsp;&nbsp;&nbsp;&nbsp;return&nbsp;</span><span style="color: #0000BB">strrev</span><span style="color: #007700">(</span><span style="color: #0000BB">md5</span><span style="color: #007700">(</span><span style="color: #0000BB">$string</span><span style="color: #007700">));<br />}<br /><br />if&nbsp;(</span><span style="color: #0000BB">$dbhandle&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #0000BB">sqlite_open</span><span style="color: #007700">(</span><span style="color: #DD0000">'mysqlitedb'</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">0666</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">$sqliteerror</span><span style="color: #007700">))&nbsp;{<br />&nbsp;&nbsp;&nbsp;&nbsp;<br />&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #0000BB">sqlite_create_function</span><span style="color: #007700">(</span><span style="color: #0000BB">$dbhandle</span><span style="color: #007700">,&nbsp;</span><span style="color: #DD0000">'md5rev'</span><span style="color: #007700">,&nbsp;</span><span style="color: #DD0000">'md5_and_reverse'</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">1</span><span style="color: #007700">);<br />&nbsp;&nbsp;&nbsp;&nbsp;<br />&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #0000BB">$sql&nbsp;&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #DD0000">'SELECT&nbsp;md5rev(filename)&nbsp;FROM&nbsp;files'</span><span style="color: #007700">;<br />&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #0000BB">$rows&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #0000BB">sqlite_array_query</span><span style="color: #007700">(</span><span style="color: #0000BB">$dbhandle</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">$sql</span><span style="color: #007700">);<br />}&nbsp;else&nbsp;{<br />&nbsp;&nbsp;&nbsp;&nbsp;echo&nbsp;</span><span style="color: #DD0000">'Error&nbsp;opening&nbsp;sqlite&nbsp;db:&nbsp;'&nbsp;</span><span style="color: #007700">.&nbsp;</span><span style="color: #0000BB">$sqliteerror</span><span style="color: #007700">;<br />&nbsp;&nbsp;&nbsp;&nbsp;exit;<br />}<br /></span><span style="color: #0000BB">?&gt;</span>
</span>
</code></div>
    </div>

   </div>
  </p>
  <p class="para">
   In this example, we have a function that calculates the md5 sum of a
   string, and then reverses it.  When the SQL statement executes, it
   returns the value of the filename transformed by our function.  The data
   returned in <em><code class="parameter">$rows</code></em> contains the processed result.
  </p>
  <p class="para">
   The beauty of this technique is that you do not need to process the
   result using a <a href="control-structures.foreach.html" class="link">foreach</a> loop after you have queried for the data.
  </p>
  <p class="para">
   PHP registers a special function named <em>php</em> when the
   database is first opened.  The php function can be used to call any PHP
   function without having to register it first.
  </p>
  <p class="para">
   <div class="example" id="example-2073">
    <p><strong>Example #2 Example of using the PHP function</strong></p>
    <div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB">&lt;?php<br />$rows&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #0000BB">sqlite_array_query</span><span style="color: #007700">(</span><span style="color: #0000BB">$dbhandle</span><span style="color: #007700">,&nbsp;</span><span style="color: #DD0000">"SELECT&nbsp;php('md5',&nbsp;filename)&nbsp;from&nbsp;files"</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?&gt;</span>
</span>
</code></div>
    </div>

    <div class="example-contents"><p>
     This example will call the <span class="function"><a href="function.md5.html" class="function">md5()</a></span> on each
     <em>filename</em> column in the database and return the result
     into <em><code class="parameter">$rows</code></em>
    </p></div>
   </div>
  </p>
  <blockquote class="note"><p><strong class="note">Note</strong>: 
   <p class="para">
    For performance reasons, PHP will not automatically encode/decode binary
    data passed to and from your UDF&#039;s.  You need to manually encode/decode
    the parameters and return values if you need to process binary data in
    this way.  Take a look at <span class="function"><a href="function.sqlite-udf-encode-binary.html" class="function">sqlite_udf_encode_binary()</a></span>
    and <span class="function"><a href="function.sqlite-udf-decode-binary.html" class="function">sqlite_udf_decode_binary()</a></span> for more details.
   </p>
  </p></blockquote>
  <div class="tip"><strong class="tip">Tip</strong>
   <p class="para">
    It is not recommended to use UDF&#039;s to handle processing of
    binary data, unless high performance is not a key requirement of your
    application.
   </p>
  </div>
  <div class="tip"><strong class="tip">Tip</strong>
   <p class="para">
    You can use <span class="function"><strong>sqlite_create_function()</strong></span> and
    <span class="function"><a href="function.sqlite-create-aggregate.html" class="function">sqlite_create_aggregate()</a></span> to override SQLite native
    SQL functions.
   </p>
  </div>
 </div>


 <div class="refsect1 seealso" id="refsect1-function.sqlite-create-function-seealso">
  <h3 class="title">参见</h3>
  <p class="para">
   <ul class="simplelist">
    <li class="member"><span class="function"><a href="function.sqlite-create-aggregate.html" class="function" rel="rdfs-seeAlso">sqlite_create_aggregate()</a> - Register an aggregating UDF for use in SQL statements</span></li>
   </ul>
  </p>
 </div>

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